Media captionHappy Feet is released - with some "gentle encouragement"

A lost emperor penguin who washed up on a New Zealand beach in June has been released back into the Southern Ocean to begin its swim home to Antarctica.

Nicknamed Happy Feet, he was released from the research vessel Tangaroa on Sunday morning about 50 miles (80km) north of the remote Campbell Island.

He was returned to the wild after recovering from surgery to remove 3kg (6.6lb) of sand from his stomach.

Last week, hundreds of people visited Wellington Zoo to bid farewell to him.

'Indescribable'

Wellington Zoo veterinarian Lisa Argilla said Happy Feet needed some "gentle encouragement" to leave the crate he had been kept in for six days while on the boat.

But he then slid down a makeshift ramp backwards and took off, she said.

"It's an indescribable feeling to see a patient finally set free. It's definitely the best part of the job," she told AFP news agency.

Happy Feet has been fitted with a tracking device so the zoo can monitor his progress.

His unexpected appearance on Peka Peka Beach - north of Wellington and 3,000km (1,860 miles) from his Antarctic colony - stunned wildlife experts who said he was only the second emperor ever recorded in New Zealand.

He is thought to have eaten the sand, having mistaken it for the snow penguins swallow to stay hydrated.